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Reproduction Growth: Egg: Immature: gradual, molts several times until it reaches adulthood 2,500+ eggs may be laid at one time by the larger orb weaver. The mass of eggs is covered with a silken sheet to produce an egg sac. Eggs are laid in the fall. In some species the eggs hatch soon, in others not until the following spring. After hatching from the egg, the spiderlings will remain in the egg sac, where they are nourished by yolk material inside their abdomen, until after their first molt. Physical Characteristics Mouthparts: Legs: Spinnerets: Eyes: Egg: Immature: chelicerate, spider jaws are tipped by fangs with a duct from a poison gland opening at the end of each 8 legs these structures are located at the base of the abdomen and are used for producing silk 8 eyes many eggs are laid within a silken egg sac white at first, gaining color with each molt Adult Color: Size: Body: each species is distinctly colored and patterned range in size from a few mm to several inches. The males are smaller than the females and can be distinguished by their dark, rounded palps (these look like little boxing gloves in front of their face). come in many shapes but those found in the Bay Area tend to have large rounded abdomens sometimes with pointed protrusions. Some Common S.F. Bay Area Species Black and Yellow Argiope (Argiope aurantia) Shamrock or Pumpkin Spider (Araneus trifolium) Banded Argiope (Argiope trifasciata) Special Adaptations Web: The intricate circular webs that these spiders build help them to capture prey. Although they can’t see very well, the spiders are sensitive to any vibrations in the web. When an insect has been caught in the sticky threads the spider wraps it in silk (before or after biting it) and carries it to the center or hub of the web to be eaten. Poison: almost all spiders have venom glands but most, including the orb weavers, are not poisonous to humans. These spiders use their venom to subdue their prey. SaveNature.Org Fir0002, flagstaffotos.com.au Sources (2) (17) (37) Orb Weaver Spiders Class Order Family Species Arachnida Araneae Araneidae 2,500+ species Range Worldwide distribution with several hundred species occurring north of Mexico Habitat Large variety of habitats from temperate to tropical, in rural as well as urban areas. Niche They build their circular webs in open areas suspended between whatever objects are available. They are often found in gardens Diet Nature: feed on insects and other arthropods caught in their webs Captivity: 1 cricket or moth or fly per week Arachnida Updated 2010: SaveNature.Org • 699 Mississippi Street • Suite 106 • San Francisco, CA 94107 • [email protected] Original: Written by Leslie Saul and Esther Julier, LITES Project, Oakland, California © National Science Foundation, 1994
